The present invention relates to valve seals for valves of internal combustion engines and, more particularly, to a valve seal retainer mechanism.
Internal combustion engines typically have a series of reciprocating valves for permitting entry of the combustion mixture into and exhaust of the combustion products out of the cylinders. These valves have valve stems which slidably reciprocate within the valve guides--bores through the cylinder head of the engine. The valves are actuated in proper sequence by means of rocker arms, push rods, cams and the like, which are well known in the art.
There typically is provided a bath of oil surrounding the above components to minimize wear during operation of the engine. In particular, it has been found that a certain amount of oil must be allowed to work its way down between the valve stem and valve guides to keep them lubricated. This prevents excessive wear of these parts. However, it is undesirable to permit excess quantities of oil to work down between the valve stems and guides since the oil will leak into the cylinder, causing excessive oil usage by the engine and poor operating characteristics.
Therefore, valve seals are typically provided which meter the amount of oil permitted between the valve stems and guides. These seals are typically positioned around the valve stems immediately above the valve guides. Some types of such seals are held in place by deformable, metallic retaining boots, such as those illustrated in U.S. Pat. No. 3,531,134, which holds the seals atop the valve guides and which telescopically and deformably engage the exposed shoulder portions of the valve guides.
The telescopic engagement between the retaining boots and the exposed shoulder portions should generally be quite tight to withstand the reciprocating forces exerted by the reciprocating valve stems over a long period of time. It has been found, however, that the retaining boots of the type illustrated in the aforementioned U.S. Pat. No. 3,531,134 will occasionally fail and pull off the exposed shoulder portions, rendering the seal useless and sometimes fouling the valve spring mechanism.
The cause of these failures is primarily attributable to relatively large tolerance ranges allowed during machining of the outside diameters of the exposed shoulders, particularly insofar as original equipment manufacture is concerned, where tolerances of .+-.0.010-inch are not uncommon. The boots, in other words, must frequently stretch over exposed shoulders with diameters considerably larger than the nominal diameters the boots were designed to fit. The boots must at the same time be capable of engaging shoulders of undersized dimension. The resultant stretching when an oversized shoulder is encountered reduces considerably the force required to pull off such boots.
Because these installation problems have been encountered, the valve seal retaining boots which are the subject of the aforementioned U.S. Pat. No. 3,531,134 have found primary acceptance only in engine rebuilding operations where tolerances are closely controlled. Such boots have not found wide acceptance by engine manufacturers as original equipment because of the noted tolerance problems. This has been the case even though metallic retaining boots of this type, when properly fitted, are far superior to any other currently available retaining boot.